Polyamidoamine dendrimer-mediated hydrogel for solubility enhancement and anti-cancer drug delivery

The application of hydrogels for anti-cancer drug delivery has garnered considerable interest in the medical field. Current cancer treatment approaches, such as chemotherapy and radiation therapy, often induce severe side effects, causing significant distress and substantial health complications to patients. Hydrogels present an appealing solution as they can be precisely injected into specific sites within the body, facilitating the sustainable release of encapsulated drugs. This localized treatment approach holds great potential for reducing toxicity levels and improving drug delivery efficacy. In this study we developed a hydrogel delivery system containing polyamidoamine (PAMAM) dendrimer and polyethylene glycol (PEG) for solubility enhancement and sustained delivery of hydrophobic anti-cancer drugs. The three selected model drugs, e.g. silibinin, camptothecin, and methotrexate, possess limited aqueous solubility and thus face restricted application. In the presence of vinyl sulfone functionalized PAMAM dendrimer at 45 mg/mL concentration, drug solubility is increased by 37-fold, 4-fold, and 10-fold for silibinin, camptothecin, and methotrexate, respectively. By further crosslinking of the functionalized PAMAM dendrimer and thiolated PEG, we successfully developed a fast-crosslinking hydrogel capable of encapsulating a significant payload of solubilized cancer drugs for sustained release. In water, the drug encapsulated hydrogels release 30%-80% of their loads in 1-4 days. MTT assays of J82 and MCF7 cells with various doses of drug encapsulated hydrogels reveal that cytotoxicity is observed for all three drugs on both J82 and MCF7 cell lines after 48 h. Notably, camptothecin exhibits higher cytotoxicity to both cell lines than silibinin and methotrexate, achieving up to 95% cell death at experimental conditions, despite its lower solubility. Our experiments provide evidence that the PAMAM dendrimer-mediated hydrogel system significantly improves the solubility of hydrophobic drugs and facilitates their sustained release. These findings position the system as a promising platform for controlled delivery of hydrophobic drugs for intratumoral cancer treatment.

Pathophysiological Aspects and Therapeutic Armamentarium of Alzheimer's Disease: Recent Trends and Future Development

Alzheimer's disease (AD) is the primary cause of dementia and is characterized by the death of brain cells due to the accumulation of insoluble amyloid plaques, hyperphosphorylation of tau protein, and the formation of neurofibrillary tangles within the cells. AD is also associated with other pathologies such as neuroinflammation, dysfunction of synaptic connections and circuits, disorders in mitochondrial function and energy production, epigenetic changes, and abnormalities in the vascular system. Despite extensive research conducted over the last hundred years, little is established about what causes AD or how to effectively treat it. Given the severity of the disease and the increasing number of affected individuals, there is a critical need to discover effective medications for AD. The US Food and Drug Administration (FDA) has approved several new drug molecules for AD management since 2003, but these drugs only provide temporary relief of symptoms and do not address the underlying causes of the disease. Currently, available medications focus on correcting the neurotransmitter disruption observed in AD, including cholinesterase inhibitors and an antagonist of the N-methyl-D-aspartate (NMDA) receptor, which temporarily alleviates the signs of dementia but does not prevent or reverse the course of AD. Research towards disease-modifying AD treatments is currently underway, including gene therapy, lipid nanoparticles, and dendrimer-based therapy. These innovative approaches aim to target the underlying pathological processes of AD rather than just managing the symptoms. This review discusses the novel aspects of pathogenesis involved in the causation of AD of AD and in recent developments in the therapeutic armamentarium for the treatment of AD such as gene therapy, lipid nanoparticles, and dendrimer-based therapy, and many more.

A new era in posterior segment ocular drug delivery: Translation of systemic, cell-targeted, dendrimer-based therapies

Vision impairment and loss due to posterior segment ocular disorders, including age-related macular degeneration and diabetic retinopathy, are a rapidly growing cause of disability globally. Current treatments consist primarily of intravitreal injections aimed at preventing disease progression and characterized by high cost and repeated clinic visits. Nanotechnology provides a promising platform for drug delivery to the eye, with potential to overcome anatomical and physiological barriers to provide safe, effective, and sustained treatment modalities. However, there are few nanomedicines approved for posterior segment disorders, and fewer that target specific cells or that are compatible with systemic administration. Targeting cell types that mediate these disorders via systemic administration may unlock transformative opportunities for nanomedicine and significantly improve patient access, acceptability, and outcomes. We highlight the development of hydroxyl polyamidoamine dendrimer-based therapeutics that demonstrate ligand-free cell targeting via systemic administration and are under clinical investigation for treatment of wet age-related macular degeneration.

Synthesis of multivalent sialyllactose-conjugated PAMAM dendrimers: Binding to SARS-CoV-2 spike protein and influenza hemagglutinin

Severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) and influenza viruses have spread around the world at an unprecedented rate. Despite multiple vaccines, new variants of SARS-CoV-2 and influenza have caused a remarkable level of pathogenesis. The development of effective antiviral drugs to treat SARS-CoV-2 and influenza remains a high priority. Inhibiting viral cell surface attachment represents an early and efficient means to block virus infection. Sialyl glycoconjugates, on the surface of human cell membranes, play an important role as host cell receptors for influenza A virus and 9-O-acetyl-sialylated glycoconjugates are receptors for MERS, HKU1 and bovine coronaviruses. We designed and synthesized multivalent 6'-sialyllactose-counjugated polyamidoamine dendrimers through click chemistry at room temperature concisely. These dendrimer derivatives have good solubility and stability in aqueous solutions. SPR, a real-time analysis quantitative method for of biomolecular interactions, was used to study the binding affinities of our dendrimer derivatives by utilizing only 200 micrograms of each dendrimer. Three SARS-CoV-2 S-protein receptor binding domain (wild type and two Omicron mutants) bound to multivalent 9-O-acetyl-6'-sialyllactose-counjugated and 6'-sialyllactose-counjugated dendrimers bound to a single H3N2 influenza A virus's HA protein (A/Hong Kong/1/1968), the SPR study results suggest their potential anti-viral activities.

Dendrimer-enabled targeted delivery attenuates glutamate excitotoxicity and improves motor function in a rabbit model of cerebral palsy

Glutamate carboxypeptidase II (GCPII), localized on the surface of astrocytes and activated microglia, regulates extracellular glutamate concentration in the central nervous system (CNS). We have previously shown that GCPII is upregulated in activated microglia in the presence of inflammation. Inhibition of GCPII activity could reduce glutamate excitotoxicity, which may decrease inflammation and promote a 'normal' microglial phenotype. 2-(3-Mercaptopropyl) pentanedioic acid (2-MPPA) is the first GCPII inhibitor that underwent clinical trials. Unfortunately, immunological toxicities have hindered 2-MPPA clinical translation. Targeted delivery of 2-MPPA specifically to activated microglia and astrocytes that over-express GCPII has the potential to mitigate glutamate excitotoxicity and attenuate neuroinflammation. In this study, we demonstrate that 2-MPPA when conjugated to generation-4, hydroxyl-terminated polyamidoamine (PAMAM) dendrimers (D-2MPPA) localize specifically in activated microglia and astrocytes only in newborn rabbits with cerebral palsy (CP), not in controls. D-2MPPA treatment led to higher 2-MPPA levels in the injured brain regions compared to 2-MPPA treatment, and the extent of D-2MPPA uptake correlated with the injury severity. D-2MPPA was more efficacious than 2-MPPA in decreasing extracellular glutamate level in ex vivo brain slices of CP kits, and in increasing transforming growth factor beta 1 (TGF-β1) level in primary mixed glial cell cultures. A single systemic intravenous dose of D-2MPPA on postnatal day 1 (PND1) decreased microglial activation and resulted in a change in microglial morphology to a more ramified form along with amelioration of motor deficits by PND5. These results indicate that targeted dendrimer-based delivery specifically to activated microglia and astrocytes can improve the efficacy of 2-MPPA by attenuating glutamate excitotoxicity and microglial activation.

Neuroendocrine control of gonadotropin-releasing hormone: Pulsatile and surge modes of secretion

The concept that different systems control episodic and surge secretion of gonadotropin-releasing hormone (GnRH) was well established by the time that GnRH was identified and formed the framework for studies of the physiological roles of GnRH, and later kisspeptin. Here, we focus on recent studies identifying the neural mechanisms underlying these two modes of secretion, with an emphasis on their core components. There is now compelling data that kisspeptin neurons in the arcuate nucleus that also contain neurokinin B (NKB) and dynorphin (i.e., KNDy cells) and their projections to GnRH dendrons constitute the GnRH pulse generator in mice and rats. There is also strong evidence for a similar role for KNDy neurons in sheep and goats, and weaker data in monkeys and humans. However, whether KNDy neurons act on GnRH dendrons and/or GnRH soma and dendrites that are found in the mediobasal hypothalamus (MBH) of these species remains unclear. The core components of the GnRH/luteinising hormone surge consist of an endocrine signal that initiates the process and a neural trigger that drives GnRH secretion during the surge. In all spontaneous ovulators, the core endocrine signal is a rise in estradiol secretion from the maturing follicle(s), with the site of estrogen positive feedback being the rostral periventricular kisspeptin neurons in rodents and neurons in the MBH of sheep and primates. There is considerable species variations in the neural trigger, with three major classes. First, in reflex ovulators, this trigger is initiated by coitus and carried to the hypothalamus by neural or vascular pathways. Second, in rodents, there is a time of day signal that originates in the suprachiasmatic nucleus and activates rostral periventricular kisspeptin neurons and GnRH soma and dendrites. Finally, in sheep nitric oxide-producing neurons in the ventromedial nucleus, KNDy neurons and rostral kisspeptin neurons all appear to participate in driving GnRH release during the surge.

Hierarchically Multivalent Peptide-Nanoparticle Architectures: A Systematic Approach to Engineer Surface Adhesion

The multivalent binding effect has been the subject of extensive studies to modulate adhesion behaviors of various biological and engineered systems. However, precise control over the strong avidity-based binding remains a significant challenge. Here, a set of engineering strategies are developed and tested to systematically enhance the multivalent binding of peptides in a stepwise manner. Poly(amidoamine) (PAMAM) dendrimers are employed to increase local peptide densities on a substrate, resulting in hierarchically multivalent architectures (HMAs) that display multivalent dendrimer-peptide conjugates (DPCs) with various configurations. To control binding behaviors, effects of the three major components of the HMAs are investigated: i) poly(ethylene glycol) (PEG) linkers as spacers between conjugated peptides; ii) multiple peptides on the DPCs; and iii) various surface arrangements of HMAs (i.e., a mixture of DPCs each containing different peptides vs DPCs cofunctionalized with multiple peptides). The optimized HMA configuration enables significantly enhanced target cell binding with high selectivity compared to the control surfaces directly conjugated with peptides. The engineering approaches presented herein can be applied individually or in combination, providing guidelines for the effective utilization of biomolecular multivalent interactions using DPC-based HMAs.

Bioinspired design of mannose-decorated globular lysine dendrimers promotes diabetic wound healing by orchestrating appropriate macrophage polarization

A large number of cytokines or growth factors have been used in the treatment of inflammation. However, they are highly dependent on an optimal delivery system with sufficient loading efficiency and protection of growth factors from proteolytic degradation. To develop the immunotherapy capacity of peptide dendrimers themselves, inspired by the structure and immunoregulatory functions of mannose-capped lipoarabinomannan (ManLAM), we thus propose a hypothesis that mannose-decorated globular lysine dendrimers (MGLDs) with precise molecular design can elicit anti-inflammatory activity through targeting and reprogramming macrophages to M2 phenotype. To achieve this, a series of mannose-decorated globular lysine dendrimers (MGLDs) was developed. Size-controlled MGLDs obtained were spherical with positive surface charges. The mean size ranged from 50-200 nm in varying generations and modification degrees. The initial screening study revealed that MGLDs have superior biocompatibility. When cocultured with MGLDs, mouse bone marrow-derived macrophages (BMDMs) acquired an anti-inflammatory M2 phenotype characterized by significant mannose receptor (MR) clustering on the cell surface and the elongated shape, an increased production of transforming growth factor (TGF)-β1, interleukin (IL)-4 and IL-10, a downregulated secretory of IL-1β, IL-6, and tumor necrosis factor (TNF)-α, and increased ability to induce fibroblast proliferation. Then in vivo studies further demonstrated that topical administration of optimized MGLDs accelerates wound repair of full-thickness cutaneous defects in type 2 diabetic mice via M2 macrophage polarization. Mechanistically, MGLDs treatment showed an enhanced closure rate, collagen deposition, and angiogenesis, along with mitigated inflammation modulated by a suppressed secretory of pro-inflammation cytokines, and increased production of TGF-β1. These findings provide the first evidence that the bioinspired design of MGLDs can direct M2 macrophage polarization, which may be beneficial in the therapy of injuries and inflammation.

Characterization of a fluorescent 1,8-naphthalimide-functionalized PAMAM dendrimer and its Cu(ii) complexes as cytotoxic drugs: EPR and biological studies in myeloid tumor cells

The activity and interacting ability of a polyamidoamine (PAMAM) dendrimer modified with 4-N-methylpiperazine-1,8-naphthalimide units (termed D) and complexed by Cu(ii) ions, towards healthy and cancer cells were studied. Comparative electron paramagnetic resonance (EPR) studies of the Cu(ii)-D complex are presented: coordination mode, chemical structure, flexibility and stability of these complexes, in the absence and presence of myeloid cancer cells and peripheral blood mononuclear cells (PBMC). The interactions of Cu(ii) ions in the biological media at different equilibrium times were studied, highlighting different stability and interacting conditions with the cells. Furthermore, flow cytometry and confocal analysis, trace the peculiar properties of the dendrimers in PBMC and U937 cells. Indeed, a new probe (Fly) was used as a potential fluorescent tool for biological imaging of Cu(ii). The study highlights that dendrimer and, mainly, the Cu(ii) metallodendrimer are cytotoxic agents for the cells, specifically for U937 tumor cells, inducing mitochondrial dysfunction, ROS increase and lysosome involvement. The metallodendrimer shows antitumor selectivity, fewer affecting healthy PBMC, inducing a massive apoptotic cell death on U937 cells, in line with the high stability of this complex, as verified by EPR studies. The results underline the potentiality of this metallodendrimer to be used as anticancer drug.

Dendrimer-Like Supramolecular Assembly of Proteins with a Tunable Size and Valency Through Stepwise Iterative Growth

The assembly of proteins in a programmable manner provides insight into the creation of novel functional nanomaterials for practical applications. Despite many advances, however, a rational protein assembly with an easy scalability in terms of size and valency remains a challenge. Here, a simple bottom-up approach to the supramolecular protein assembly with a tunable size and valency in a programmable manner is presented. The dendrimer-like protein assembly, simply called a "protein dendrimer," is constructed through a stepwise and alternate addition of a building block protein. Starting from zeroth-generation protein dendrimer (pG0 ) of 27 kDa, the protein dendrimer is sequentially grown to pG1 , pG2 , pG3 , to pG4 with a molecular mass of 94, 216, 483, and 959 kDa, respectively. The valency of the protein dendrimers at the periphery increases by a factor of two after each generation, allowing a tunable valency and easy functionalization. The protein dendrimers functionalizes with a targeting moiety and a cytotoxic protein cargo shows a typical feature of multi-valency in the avidity and a highly enhanced cellular cytotoxicity, exemplifying their utility as a protein delivery platform. The present approach can be effectively used in the creation of protein architectures with new functions for biotechnological and medical applications.

In vitro/vivo antitumor study of modified-chitosan/carboxymethyl chitosan "boosted" charge-reversal nanoformulation

Major obstacles in the development of nanoformulations as efficient drug delivery systems are the rapid clearance from blood circulation and lysosomal entrapment. To overcome these problems, a polysaccharide-based core-shell type charge-switchable nanoformulation (CS-LA-DMMA/CMCS/PAMAM@DOX) is constructed to improve antitumor efficacy of DOX. By applying carboxymethyl chitosan (CMCS) as bridge polymer and negatively charged chitosan-derivative as outer shell, the stability and pH-sensitivity of this nanoformulation is promisingly enhanced. Furthermore, the positively charged PAMAM@DOX could escape from lysosomes via "proton sponge effect" and "cationic-anionic interaction with lysosome membranes". Admirable cellular uptake and high apoptosis/necrosis rate were detected in this study. In vitro assays demonstrate that the CS-LA-DMMA/CMCS/PAMAM@DOX was internalized into HepG2 cells predominantly via the clathrin-mediated endocytosis pathway. Excitingly, in vivo studies showed that high accumulation of CS-LA-DMMA/CMCS/PAMAM@DOX in tumor tissue led to enhanced tumor inhibition. Compared with free DOX, the tumor inhibition rate of nanoformulation was improved up to 226%.

Dendronized hyaluronic acid-docetaxel conjugate as a stimuli-responsive nano-agent for breast cancer therapy

To achieve target delivery of anti-tumor drugs with great biocompatibility into tumor tissues, a stimuli-responsive dendronized hyaluronic acid (HA)-docetaxel conjugate (HA-DTX-Dendron, HADD) was designed and prepared. The incorporation of HA in HADD improved the delivery of DTX to tumor cells with rich CD44 receptors. Enhanced biocompatibility and therapeutic outcomes were achieved using glyodendrons-modified HA and tumor microenvironment-responsive linkers in HADD. The glycodendron was connected with HA via GSH-responsive disulfide bonds, and the drug DTX was linked to the carrier via a cathepsin B-responsive tetrapeptide GFLG. This design resulted in self-assembly nanostructures for facilitating uptake of HADD by tumor cells and rapid release of DTX to exert its therapeutic effect. Compared to free DTX, HADD showed much higher tumor growth inhibition in the MDA-MB-231 tumor-bearing mice model (up to 99.71%), and no toxicity was observed. Therefore, HADD could be employed as an efficacious nano-agent for treating triple negative breast cancer (TNBC).

Plasma Corona Protects Human Immune Cells from Structurally Nanoengineered Antimicrobial Peptide Polymers

Safe and effective antimicrobials are needed to combat emerging antibiotic-resistant bacteria. Structurally nanoengineered antimicrobial peptide polymers (termed SNAPPs) interact with bacterial cell membranes to potently kill bacteria but may also interact at some level with human cell membranes. We studied the association of four different SNAPPs with six different white blood cells within fresh whole human blood by flow cytometry. In whole human blood, SNAPPs had detectable association with phagocytic cells and B cells, but not natural killer and T cells. However, without plasma proteins and therefore no protein corona on the SNAPPs, a greater marked association of SNAPPs with all white blood cell types was detected, resulting in cytotoxicity against most blood cell components. Thus, the formation of a protein corona around the SNAPPs reduced the association and prevented human blood cell cytotoxicity of the SNAPPs. Understanding the bio-nano interactions of these SNAPPs will be crucial to ensuring that the design of next-generation SNAPPs and other promising antimicrobial nanomaterials continues to display high efficacy toward antibiotic-resistant bacteria while maintaining a low toxicity to primary human cells.

Silencing of HMGA2 by siRNA Loaded Methotrexate Functionalized Polyamidoamine Dendrimer for Human Breast Cancer Cell Therapy

The transcription factor high mobility group protein A2 (HMGA2) plays an important role in the pathogenesis of some cancers including breast cancer. Polyamidoamine dendrimer generation 4 is a kind of highly branched polymeric nanoparticle with surface charge and highest density peripheral groups that allow ligands or therapeutic agents to attach it, thereby facilitating target delivery. Here, methotrexate (MTX)- modified polyamidoamine dendrimer generation 4 (G4) (G4/MTX) was generated to deliver specific small interface RNA (siRNA) for suppressing HMGA2 expression and the consequent effects on folate receptor (FR) expressing human breast cancer cell lines (MCF-7, MDA-MB-231). We observed that HMGA2 siRNA was electrostatically adsorbed on the surface of the G4/MTX nanocarrier for constructing a G4/MTX-siRNA nano-complex which was verified by changing the final particle size and zeta potential. The release of MTX and siRNA from synthesized nanocomplexes was found in a time- and pH-dependent manner. We know that MTX targets FR. Interestingly, G4/MTX-siRNA demonstrates significant cellular internalization and gene silencing efficacy when compared to the control. Besides, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay demonstrated selective cell cytotoxicity depending on the folate receptor expressing in a dose-dependent manner. The gene silencing and protein downregulation of HMGA2 by G4/MTX-siRNA was observed and could significantly induce cell apoptosis in MCF-7 and MDA-MB-231 cancer cells compared to the control group. Based on the findings, we suggest that the newly developed G4/MTX-siRNA nano-complex may be a promising strategy to increase apoptosis induction through HMGA2 suppression as a therapeutic target in human breast cancer.

First-in-class and best-in-class dendrimer nanoplatforms from concept to clinic: Lessons learned moving forward

Research to develop active dendrimers by themselves or as nanocarriers represents a promising approach to discover new biologically active entities that can be used to tackle unmet medical needs including difficult diseases. These developments are possible due to the exceptional physicochemical properties of dendrimers, including their biocompatibility, as well as their therapeutic activity as nanocarriers and drugs themselves. Despite a large number of academic studies, very few dendrimers have crossed the 'valley of death' between. Only a few number of pharmaceutical companies have succeeded in this way. In fact, only Starpharma (Australia) and Orpheris, Inc. (USA), an Ashvattha Therapeutics subsidiary, can fill all the clinic requirements to have in the market dendrimers based drugs/nancocarriers. After evaluating the main physicochemical properties related to the respective biological activity of dendrimers classified as first-in-class or best-in-class in nanomedicine, this original review analyzes the advantages and disavantages of these two strategies as well the concerns to step in clinical phases. Various solutions are proposed to advance the use of dendrimers in human health.

Molecular exclusion limits for diffusion across a porous capsid

Molecular communication across physical barriers requires pores to connect the environments on either side and discriminate between the diffusants. Here we use porous virus-like particles (VLPs) derived from bacteriophage P22 to investigate the range of molecule sizes able to gain access to its interior. Although there are cryo-EM models of the VLP, they may not accurately depict the parameters of the molecules able to pass across the pores due to the dynamic nature of the P22 particles in the solution. After encapsulating the enzyme AdhD within the P22 VLPs, we use a redox reaction involving PAMAM dendrimer modified NADH/NAD+ to examine the size and charge limitations of molecules entering P22. Utilizing the three different accessible morphologies of the P22 particles, we determine the effective pore sizes of each and demonstrate that negatively charged substrates diffuse across more readily when compared to those that are neutral, despite the negatively charge exterior of the particles.

Cationic Dendrimers for siRNA Delivery: An Overview of Methods for In Vitro/In Vivo Characterization

This chapter reviews the different techniques for analyzing the chemical-physical properties, transfection efficiency, cytotoxicity, and stability of covalent cationic dendrimers (CCDs) and self-assembled cationic dendrons (ACDs) for siRNA delivery in the presence and absence of their nucleic cargos. On the basis of the reported examples, a standard essential set of techniques is described for each step of a siRNA/nanovector (NV) complex characterization process: (1) analysis of the basic chemical-physical properties of the NV per se; (2) characterization of the morphology, size, strength, and stability of the siRNA/NV ensemble; (3) characterization and quantification of the cellular uptake and release of the siRNA fragment; (4) in vitro and (5) in vivo experiments for the evaluation of the corresponding gene silencing activity; and (6) assessment of the intrinsic toxicity of the NV and the siRNA/NV complex.

Treatment of acute lung inflammation by pulmonary delivery of anti-TNF-α siRNA with PAMAM dendrimers in a murine model

To improve the efficacy of nucleic acid-based therapeutics, e.g., small interfering RNA (siRNA), transfection agents are needed for efficient delivery into cells. Several classes of dendrimers have been found useful as transfection agents for the delivery of siRNA because their surface can readily be functionalized, and the size of the dendriplexes they form with siRNA is within the range of conventional nanomedicine. In this study, commercially available generation 3 poly(amidoamine) (PAMAM) dendrimer was investigated for pulmonary delivery of siRNA directed against tumor necrosis factor (TNF) α for the treatment of acute lung inflammation. Delivery efficiency was assessed in vitro in the RAW264.7 macrophage cell line activated with lipopolysaccharide (LPS), and efficacy was evaluated in vivo in a murine model of LPS-induced lung inflammation upon pre-treatment with TNF-α siRNA. The PAMAM dendrimer-siRNA complexes (dendriplexes) displayed strong siRNA condensation and high cellular uptake in macrophages compared with non-complexed siRNA. Q-PCR analyses showed that the dendriplexes mediated efficient and specific TNF-α silencing in vitro, as compared to non-complexed siRNA and dendriplexes with negative control siRNA. Also in vivo, the PAMAM dendriplexes induced efficacious TNF-α siRNA inhibition, as compared to non-complexed siRNA, upon pulmonary administration to mice with LPS-induced lung inflammation. Hence, these data suggest that PAMAM dendrimers are promising for the local delivery of TNF-α siRNA in the treatment of lung inflammation via pulmonary administration.

Dendrimer-Functionalized Hybrid Materials Based on Silica as Novel Carriers of Bioactive Acids

One of the major goals in the materials science is the design and development of non-toxic, versatile, and efficient drug delivery systems. The study reported in this paper concerns the syntheses of poly(amidoamine) (PAMAM) dendrimers with tris(2-aminoethyl)amine as an amine core and different terminal amines, and their attachment to silica matrix. The obtained ethylenediamine (EDA), triethylenetetramine (TETA), tris(2-aminoethyl)amine (TREN) and 4,7,10-trioxa-1,13-tridecanediamine (TRI-OXA) dendrimers were introduced to the support surface via an epoxy linker, leading to a loading efficiency in the range of 0.054–0.113 mmol g⁻¹, determined using elemental and thermogravimetric analyses. The materials exhibited high adsorption capacities towards the chosen model drugs: folic, salicylic and nicotinic acid. The investigated adsorption processes were found to follow the Freundlich isotherm model, with indication of the drugs’ structure influence on the binding efficiency. Drug-loaded hybrid materials were also described for in vitro drug release in three pH-different paraphysiological media. The highest percentage release was obtained in the tests performed at pH 2.0, ranging between 35.42 and 99.83%. Satisfactory results and the versatility of PAMAM dendrimers may lead to the application of such materials not only as drug carriers dedicated to a wide range of pharmaceutics, but also as analytical tools for pre-concentration and/or the determination of biocompound contamination in samples.

The Effect of Biotinylated PAMAM G3 Dendrimers Conjugated with COX-2 Inhibitor (celecoxib) and PPARγ Agonist (Fmoc-L-Leucine) on Human Normal Fibroblasts, Immortalized Keratinocytes and Glioma Cells in Vitro

Glioblastoma multiforme (GBM) is the most malignant type of central nervous system tumor that is resistant to all currently used forms of therapy. Thus, more effective GBM treatment strategies are being investigated, including combined therapies with drugs that may cross the blood brain barrier (BBB). Another important issue considers the decrease of deleterious side effects of therapy. It has been shown that nanocarrier conjugates with biotin can penetrate BBB. In this study, biotinylated PAMAM G3 dendrimers substituted with the recognized anticancer agents cyclooxygenase-2 (COX-2) inhibitor celecoxib and peroxisome proliferator-activated receptor γ (PPARγ) agonist Fmoc-L-Leucine (G3-BCL) were tested in vitro on human cell lines with different p53 status: glioblastoma (U-118 MG), normal fibroblasts (BJ) and immortalized keratinocytes (HaCaT). G3-BCL penetrated efficiently into the lysosomal and mitochondrial compartments of U-118 MG cells and induced death of U-118 MG cells via apoptosis and inhibited proliferation and migration at low IC₅₀ = 1.25 µM concentration, considerably lower than either drug applied alone. Comparison of the effects of G3-BCL on expression of COX-2 and PPARγ protein and PGE₂ production of three different investigated cell line phenotypes revealed that the anti-glioma effect of the conjugate was realized by other mechanisms other than influencing PPAR-γ expression and regardless of p53 cell status, it was dependent on COX-2 protein level and high PGE₂ production. Similar G3-BCL cytotoxicity was seen in normal fibroblasts (IC₅₀ = 1.29 µM) and higher resistance in HaCaT cells (IC₅₀ = 4.49 µM). Thus, G3-BCL might be a good candidate for the targeted, local glioma therapy with limited site effects.

Dendrimer Conjugation Enables Multiphoton Chemical Neurophysiology Studies with an Extended π-Electron Caging Chromophore

We have developed a caged neurotransmitter using an extended π-electron chromophore for efficient multiphoton uncaging on living neurons. Widely studied in a chemical context, such chromophores are inherently bioincompatible due to their highly lipophilic character. Attachment of two polycarboxylate dendrimers, a method we call "cloaking", to a bisstyrylthiophene (or BIST) core effectively transformed the chromophore into a water-soluble optical probe, whilst maintaining the high two-photon absorption of over 500 GM. Importantly, the cloaked caged compound was biologically inert at the high concentrations required for multiphoton chemical physiology. Thus, in contrast to non-cloaked BIST compounds, the BIST-caged neurotransmitter can be safely delivered onto neurons in acutely isolated brain slices, thereby enabling high-resolution two-photon uncaging without any side effects. We expect that our cloaking method will enable the development of new classes of cell-compatible photolabile probes using a wide variety of extended π-electron caging chromophores.

Membrane-Mimetic Dendrimersomes Engulf Living Bacteria via Endocytosis

There is much interest in developing vesicular microcompartments from natural and synthetic amphiphiles, enabling programmable interactions with living matter. Of particular interest is the development of vesicles capable of endocytosis of living bacteria. Despite the complexity of this process, theoretical studies predict that the endocytosis of prolate micro-objects is possible without the need of active cell machinery if the energy released upon bacterial adhesion to the membrane surpasses the energy required to bend the membrane. Nonetheless, natural liposomes and synthetic polymersomes fail to sufficiently recapitulate membrane properties to perform this advanced function. Here we report the engulfment of living bacteria into endosomes by cell-like dendrimersomes assembled from Janus dendrimers. Full engulfment occurred in less than a minute after contact. The process is driven by the adhesion of the bacterium to the dendrimersome's membrane by ultraweak interactions, comparable to those utilized by nature. The key to success relies on the combination of high flexibility and stability of the dendrimersomes. The key properties of the dendrimersomes are programmed into the molecular structures of their building blocks. The ability to support endocytosis highlights opportunities for the design and programming of dendrimersomes in biomedical research.

Tunable Hydrophile-Lipophile Balance for Manipulating Structural Stability and Tumor Retention of Amphiphilic Nanoparticles

Hydrophile-lipophile balance (HLB) has a great influence on the self-assembly and physicochemical properties of amphiphiles, thus affecting their biological effects. It is shown that amphiphilic nanoparticles (NPs) with a moderate HLB value display enhanced stability and highly efficient tumor retention. 2,2-Bis(hydroxymethyl)propionic acid hyperbranched poly(ethylene glycol) (PEG)-pyropheophorbide-a (Ppa) amphiphiles (G320P, G310P, G220P, and G210P) are synthesized with a tunable HLB value from 6.1 to 9.9 by manipulating the number of generation of dendrons (G2 or G3) and the molecular weight of PEG chains (10 or 20 kDa). Molecular dynamics simulations reveal that G320P and G210P with a moderate HLB value (8.0 and 7.8) self-assemble into very stable NPs with a small solvent accessible surface area and high nonbonding interactions. G320P with a moderate HLB value (8.0) and a long PEG chain excels against other NPs in prolonging the blood circulation time of Ppa (up to 13-fold), penetrating deeply into multicellular tumor spheroids and accumulating in tumors, and enhancing the PDT efficacy with a tumor growth inhibition of 96.0%. Rational design of NPs with a moderate HLB value may be implemented in these NP-derived nanomedicines to achieve high levels of retention in tumors.

Encapsulation of anticancer drug doxorubicin inside dendritic macromolecular cavities: First-principles benchmarks

By using first-principles approaches based on Density Functional Theory, we explore the possibility of using dendritic macromolecular structures as carriers of the doxorubicin anticancer drug. In particular, we consider macromolecular cavities of different sizes composed of phenylene-, thiophene-, phenyl-cored thiophen- and thioazole-based dendrimers. The comparison between the optimized molecular geometries of the monomers and of the host-guest complexes reveals that only slight structural changes are observed in doxorubicin upon complexation. Also, the encapsulation energies for the host-guest complexes suggest that these systems are of potential use for pharmacology applications in vivo. The interaction of the guest doxorubicin with the macromolecular cavities exploits different types of weak intermolecular forces including σ, π and hydrogen bond interactions. The electronic structure of these complexes is discussed, with particular emphasis placed on the role of the charge distribution and the nature of the frontier molecular orbitals in the encapsulation process. Spectroscopic properties of these complexes are derived to facilitate their detection in laboratory and in vivo. These include IR vibrational frequencies, absorption wavelengths and relative oscillator strengths for the main transitions in the UV-Vis spectrum.

A boronic acid-rich dendrimer with robust and unprecedented efficiency for cytosolic protein delivery and CRISPR-Cas9 gene editing

Cytosolic protein delivery is of central importance for the development of protein-based biotechnologies and therapeutics; however, efficient intracellular delivery of native proteins remains a challenge. Here, we reported a boronic acid-rich dendrimer with unprecedented efficiency for cytosolic delivery of native proteins. The dendrimer could bind with both negatively and positively charged proteins and efficiently delivered 13 cargo proteins into the cytosol of living cells. All the delivered proteins kept their bioactivities after cytosolic delivery. The dendrimer ensures efficient intracellular delivery of Cas9 protein into various cell lines and showed high efficiency in CRISPR-Cas9 genome editing. The rationally designed boronic acid-rich dendrimer permits the development of an efficient platform with high generality for the delivery of native proteins.

ROS-Response-Induced Zwitterionic Dendrimer for Gene Delivery

As one of the most promising therapeutic methods, gene therapy has been playing a more and more important role in treating disease due to its ultra-high therapy efficiency. Even if nonviral gene vectors represented by polycation, liposomal, dendrimers, and zwitterionic materials have made great progress in gene complexation, low immunogenicity, and biocompatibility, intracellular gene release with low toxicity is effectively still a bottleneck restricting the clinical application of gene therapy. We designed and synthesized a reactive oxygen species (ROS)-responsive dendrimer poly(amido amine)- N-(4-boronobenzyl)- N, N-diethyl-2-(propionyloxy)ethan-1-aminium (PAMAM-(B-DEAEP)₁₆) as a gene vector whose potential can vary from positive to negative under the elevated ROS (H₂O₂) in cancerous cells. Dynamic light scattering results showed that the zeta potential of PAMAM-(B-DEAEP)₁₆ decreased from +12.3 to -5 mV under 80 mM H₂O₂ in PBS buffer. The ¹H NMR results demonstrated that the intermediate status of PAMAM-(B-DEAEP)₁₆ was zwitterionic in ∼6 h because it consisted of the positive quaternary ammonium and negative carboxylic acid simultaneously before the ester bond was completely hydrolyzed. Gel retardation assay showed that PAMAM-(B-DEAEP)₁₆ can condense DNA at above N/P = 1; then, PAMAM-(B-DEAEP)₁₆ transfers to zwitterionic, which begins to continuously release DNA with the decrease in the positive charges and increase in the negative charges, and finally to negatively charged poly(amido amine)-propionic acid (PAMAM-PAc₁₆) in the 80 mM H₂O₂. Fluorescence-labeled Cy-5 DNA indicated that PAMAM-(B-DEAEP)₁₆ can enter into the cell completely in ∼4 h. The results showed that this compound we designed exhibited higher gene transfection efficiency and lower cytotoxicity than commercial PEI. This is the first time that the positively charged dendrimer was transferred to zwitterionic dendrimer under the stimuli of H₂O₂ and was successfully applied to gene delivery. Unlike all of the previous reports, we did not seek a compromise between the high gene transfection and low toxicity but find a new avenue to make the gene carrier not only have higher gene transfection efficiency but also exhibit lower toxicity by introducing stimuli-sensitive groups into the positively charged dendrimer to make it capable of adjusting the charge property according to the microenvironment. This study not only provides a good method to design materials for gene delivery but also opens a new perspective to understand the process of gene delivery.

PAMAM dendrimers: blood-brain barrier transport and neuronal uptake after focal brain ischemia

Drug delivery to the central nervous system is restricted by the blood-brain barrier (BBB). However, with the onset of stroke, the BBB becomes leaky, providing a window of opportunity to passively target the brain. Here, cationic poly(amido amine) (PAMAM) dendrimers of different generations were functionalized with poly(ethylene glycol) (PEG) to reduce cytotoxicity and prolong blood circulation half-life, aiming for a safe in vivo drug delivery system in a stroke scenario. Rhodamine B isothiocyanate (RITC) was covalently tethered to the dendrimer backbone and used as a small surrogate drug as well as for tracking purposes. The biocompatibility of PAMAM was markedly increased by PEGylation as a function of dendrimer generation and degree of functionalization. The PEGylated RITC-modified dendrimers did not affect the integrity of an in vitro BBB model. Additionally, the functionalized dendrimers remained safe when in contact with the bEnd.3 cells and rat primary astrocytes composing the in vitro BBB model after hypoxia induced by oxygen-glucose deprivation. Modification with PEG also decreased the interaction and uptake by endothelial cells of PAMAM, indicating that the transport across a leaky BBB due to focal brain ischemia would be facilitated. Next, the functionalized dendrimers were tested in contact with red blood cells showing no haemolysis for the PEGylated PAMAM, in contrast to the unmodified dendrimer. Interestingly, the PEG-modified dendrimers reduced blood clotting, which may be an added beneficial function in the context of stroke. The optimized PAMAM formulation was intravenously administered in mice after inducing permanent focal brain ischemia. Twenty-four hours after administration, dendrimers could be detected in the brain, including in neurons of the ischemic cortex. Our results suggest that the proposed formulation has the potential for becoming a successful delivery vector for therapeutic application to the injured brain after stroke reaching the ischemic neurons.

Targeting Mitochondrial Dysfunction and Oxidative Stress in Activated Microglia using Dendrimer-Based Therapeutics

Mitochondrial oxidative stress is associated with many neurodegenerative diseases, such as traumatic brain injury (TBI). Targeted delivery of antioxidants to mitochondria has failed to translate into clinical success due to their nonspecific cellular localization, poor transport properties across multiple biological barriers, and associated side effects. These challenges, coupled with the complex function of the mitochondria, create the need for innovative delivery strategies. Methods: Neutral hydroxyl-terminated polyamidoamine (PAMAM) dendrimers have shown significant potential as nanocarriers in multiple brain injury models. N-acetyl cysteine (NAC) is a clinically used antioxidant and anti-inflammatory agent which has shown significant potency when delivered in a targeted manner. Here we present a mitochondrial targeting hydroxyl PAMAM dendrimer-drug construct (TPP-D-NAC) with triphenyl-phosphonium (TPP) for mitochondrial targeting and NAC for targeted delivery to mitochondria in injured glia. Co-localization and mitochondrial content of mitochondria-targeted and unmodified dendrimer were assessed in microglia and macrophages in vitro via immunohistochemistry and fluorescence quantification. Therapeutic improvements of TPP-D-NAC over dendrimer-NAC conjugate (D-NAC) and free NAC were evaluated in vitro in microglia under oxidative stress challenge. In vivo neuroinflammation targeting was confirmed in a rabbit model of TBI. Results: TPP-conjugated dendrimer co-localized significantly more with mitochondria than unmodified dendrimer without altering overall levels of cellular internalization. This targeting capability translated to significant improvements in the attenuation of oxidative stress by TPP-D-NAC compared to D-NAC and free NAC. Upon systemic administration in a rabbit TBI model, TPP-conjugated dendrimer co-localized specifically with mitochondria in activated microglia and macrophages in the white matter of the ipsilateral/injured hemisphere, confirming its BBB penetration and glial targeting capabilities. Conclusion: D-NAC has shown promising efficacy in many animal models of neurodegeneration, and this work provides evidence that modification for mitochondrial targeting can further enhance its therapeutic efficacy, particularly in diseases where oxidative stress-induced glial cell death plays a significant role in disease progression.

Computational calculation identified optimal binding sites in nano-sized magnetic-cored dendrimer

Magnetic-cored dendrimers (MDs) with amino groups were prepared with the formation of poly(amidoamine) dendrimer on the surface of magnetite nanoparticles (MNPs). The experiment involved the binding of four different heavy metal ions including Pb (II), Cu (II), Zn (II), and Cr (VI). Density functional theory (DFT) calculation was applied to the experimental results to determine the optimal configurations between the heavy metal species and generation 1 amino (NH₂) functionalized MD (G1-NH₂-MD). Different binding configurations among the possible binding positions of inner and outer G1-NH₂-MD were determined with the ionic radius and coordination number of each heavy metal ion. Although Pb²⁺ and Zn²⁺ were stable in the terminal positions, Cu²⁺ was the most stable in the internal position. The oxygen and hydrogen atoms of HCrO₄^- formed a hydrogen bond with the NH₂ groups, and thus dipole-nonpolar molecular interaction occurred with the CH₂ groups of G1-NH₂-MD. Specific binding positions and energies of different heavy metal species were identified through the DFT calculation in the study. The DFT calculation results also contributed to an understanding of the binding priority of each metal ions in the mixed solution. Furthermore, Pb²⁺ was preferably adsorbed in the mixed solution of Pb²⁺, Cu²⁺, and Zn²⁺.

Effect of Dendrimer Generation and Aglyconic Linkers on the Binding Properties of Mannosylated Dendrimers Prepared by a Combined Convergent and Onion Peel Approach

An efficient study of carbohydrate-protein interactions was achieved using multivalent glycodendrimer library. Different dendrimers with varied peripheral sugar densities and linkers provided an arsenal of potential novel therapeutic agents that could be useful for better specific action and greater binding affinities against their cognate protein receptors. Highly effective click chemistry represents the basic method used for the synthesis of mannosylated dendrimers. To this end, we used propargylated scaffolds of varying sugar densities ranging from 2 to 18 for the attachment of azido mannopyranoside derivatives using copper catalyzed click cycloaddition. Mannopyranosides with short and pegylated aglycones were used to evaluate their effects on the kinetics of binding. The mannosylated dendrons were built using varied scaffolds toward the accelerated and combined "onion peel" strategy These carbohydrates have been designed to fight E. coli urinary infections, by inhibiting the formation of bacterial biofilms, thus neutralizing the adhesion of FimH type 1 lectin present at the tip of their fimbriae against the natural multiantennary oligomannosides of uroplakin 1a receptors expressed on uroepithelial tissues. Preliminary DLS studies of the mannosylated dendrimers to cross- link the leguminous lectin Con A used as a model showed their high potency as candidates to fight the E. coli adhesion and biofilm formation.

Dendrimer-paclitaxel complexes for efficient treatment in ovarian cancer: study on OVCAR-3 and HEK293T cells

The present paper investigates the enhancement of the therapeutic effect of Paclitaxel (a potent anticancer drug) by increasing its cellular uptake in the cancerous cells with subsequent reduction in its cytotoxic effects. To fulfill these goals the Paclitaxel (PTX)-Biotinylated PAMAM dendrimer complexes were prepared using biotinylation method. The primary parameter of Biotinylated PAMAM with a terminal HN₂ group - the degree of biotinylation - was evaluated using HABA assay. The basic integrity of the complex was studied using DSC. The Drug Loading (DL) and Drug Release (DR) parameters of Biotinylated PAMAM dendrimer-PTX complexes were also examined. Cellular uptake study was performed in OVCAR-3 and HEK293T cells using fluorescence technique. The statistical analysis was also performed to support the experimental data. The results obtained from HABA assay showed the complete biotinylation of PAMAM dendrimer. DSC study confirmed the integrity of the complex as compared with pure drug, biotinylated complex and their physical mixture. Batch 9 showed the highest DL (12.09%) and DR (70%) for 72 h as compared to different concentrations of drug and biotinylated complex. The OVCAR-3 (cancerous) cells were characterized by more intensive cellular uptake of the complexes than HEK293T (normal) cells. The obtained experimental results were supported by the statistical data. The results obtained from both experimental and statistical evaluation confirmed that the biotinylated PAMAM NH₂ dendrimer-PTX complex not only displays increased cellular uptake but has also enhanced release up to 72 h with the reduction in cytotoxicity.

Cloaked Caged Compounds: Chemical Probes for Two-Photon Optoneurobiology

Caged neurotransmitters, in combination with focused light beams, enable precise interrogation of neuronal function, even at the level of single synapses. However, most caged transmitters are, surprisingly, severe antagonists of ionotropic gamma-aminobutyric acid (GABA) receptors. By conjugation of a large, neutral dendrimer to a caged GABA probe we introduce a "cloaking" technology that effectively reduces such antagonism to very low levels. Such cloaked caged compounds will enable the study of the signaling of the inhibitory neurotransmitter GABA in its natural state using two-photon uncaging microscopy for the first time.

Time-Resolved Fluorescence Spectroscopy and Fluorescence Lifetime Imaging Microscopy for Characterization of Dendritic Polymer Nanoparticles and Applications in Nanomedicine

The emerging field of nanomedicine provides new approaches for the diagnosis and treatment of diseases, for symptom relief and for monitoring of disease progression. One route of realizing this approach is through carefully constructed nanoparticles. Due to the small size inherent to the nanoparticles a proper characterization is not trivial. This review highlights the application of time-resolved fluorescence spectroscopy and fluorescence lifetime imaging microscopy (FLIM) for the analysis of nanoparticles, covering aspects ranging from molecular properties to particle detection in tissue samples. The latter technique is particularly important as FLIM allows for distinguishing of target molecules from the autofluorescent background and, due to the environmental sensitivity of the fluorescence lifetime, also offers insights into the local environment of the nanoparticle or its interactions with other biomolecules. Thus, these techniques offer highly suitable tools in the fields of particle development, such as organic chemistry, and in the fields of particle application, such as in experimental dermatology or pharmaceutical research.

The Role of Galectin-1 in Cancer Progression, and Synthetic Multivalent Systems for the Study of Galectin-1

This review discusses the role of galectin-1 in the tumor microenvironment. First, the structure and function of galectin-1 are discussed. Galectin-1, a member of the galectin family of lectins, is a functionally dimeric galactoside-binding protein. Although galectin-1 has both intracellular and extracellular functions, the defining carbohydrate-binding role occurs extracellularly. In this review, the extracellular roles of galectin-1 in cancer processes are discussed. In particular, the importance of multivalent interactions in galectin-1 mediated cellular processes is reviewed. Multivalent interactions involving galectin-1 in cellular adhesion, mobility and invasion, tumor-induced angiogenesis, and apoptosis are presented. Although the mechanisms of action of galectin-1 in these processes are still not well understood, the overexpression of galectin-1 in cancer progression indicates that the role of galectin-1 is significant. To conclude this review, synthetic frameworks that have been used to modulate galectin-1 processes are reviewed. Small molecule oligomers of carbohydrates, carbohydrate-functionalized pseudopolyrotaxanes, cyclodextrins, calixarenes, and glycodendrimers are presented. These synthetic multivalent systems serve as important tools for studying galectin-1 mediated cancer cellular functions.

Arginine-glycine-aspartic acid-polyethylene glycol-polyamidoamine dendrimer conjugate improves liver-cell aggregation and function in 3-D spheroid culture

The polyamidoamine (PAMAM) dendrimer, a type of macromolecule material, has been used in spheroidal cell culture and drug delivery in recent years. However, PAMAM is not involved in the study of hepatic cell-spheroid culture or its biological activity, particularly in detoxification function. Here, we constructed a PAMAM-dendrimer conjugate decorated by an integrin ligand: arginine-glycine-aspartic acid (RGD) peptide. Our studies demonstrate that RGD-polyethylene glycol (PEG)-PAMAM conjugates can promote singly floating hepatic cells to aggregate together in a sphere-like growth with a weak reactive oxygen species. Moreover, RGD-PEG-PAMAM conjugates can activate the AKT-MAPK pathway in hepatic cells to promote cell proliferation and improve basic function and ammonia metabolism. Together, our data support the hepatocyte sphere treated by RGD-PEG-PAMAM conjugates as a potential source of hepatic cells for a biological artificial liver system.

Dendrimer-Based Selective Proteostasis-Inhibition Strategy to Control NSCLC Growth and Progression

Elevated valosin containing protein (VCP/p97) levels promote the progression of non-small cell lung carcinoma (NSCLC). Although many VCP inhibitors are available, most of these therapeutic compounds have low specificity for targeted tumor cell delivery. Hence, the primary aim of this study was to evaluate the in vitro efficacy of dendrimer-encapsulated potent VCP-inhibitor drug in controlling non-small cell lung carcinoma (NSCLC) progression. The VCP inhibitor(s) (either in their pure form or encapsulated in generation-4 PAMAM-dendrimer with hydroxyl surface) were tested for their in vitro efficacy in modulating H1299 (NSCLC cells) proliferation, migration, invasion, apoptosis and cell cycle progression. Our results show that VCP inhibition by DBeQ was significantly more potent than NMS-873 as evident by decreased cell proliferation (p<0.0001, MTT-assay) and migration (p<0.05; scratch-assay), and increased apoptosis (p<0.05; caspase-3/7-assay) as compared to untreated control cells. Next, we found that dendrimer-encapsulated DBeQ (DDNDBeQ) treatment increased ubiquitinated-protein accumulation in soluble protein-fraction (immunoblotting) of H1299 cells as compared to DDN-control, implying the effectiveness of DBeQ in proteostasis-inhibition. We verified by immunostaining that DDNDBeQ treatment increases accumulation of ubiquitinated-proteins that co-localizes with an ER-marker, KDEL. We observed that proteostasis-inhibition with DDNDBeQ, significantly decreased cell migration rate (scratch-assay and transwell-invasion) as compared to the control-DDN treatment (p<0.05). Moreover, DDNDBeQ treatment showed a significant decrease in cell proliferation (p<0.01, MTT-assay) and increased caspase-3/7 mediated apoptotic cell death (p<0.05) as compared to DDN-control. This was further verified by cell cycle analysis (propidium-iodide-staining) that demonstrated significant cell cycle arrest in the G2/M-phase (p<0.001) by DDNDBeQ treatment as compared to control-DDN. Moreover, we confirmed by clonogenic-assay that DDNDBeQ treatment significantly (p<0.001) inhibits H1299 colony-formation as compared to control/DDN. Overall, encapsulation of potent VCP-inhibitor DBeQ into a dendrimer allows selective VCP-mediated proteostasis-inhibition for controlling NSCLC-tumor growth and progression to allow tumor-targeted sustained drug delivery.

Self-Assembly of Amphiphilic Dendrimers: The Role of Generation and Alkyl Chain Length in siRNA Interaction

An ideal nucleic-acid transfection system should combine the physical and chemical characteristics of cationic lipids and linear polymers to decrease cytotoxicity and uptake limitations. Previous research described new types of carriers termed amphiphilic dendrimers (ADs), which are based on polyamidoamine dendrimers (PAMAM). These ADs display the cell membrane affinity advantage of lipids and preserve the high affinity for DNA possessed by cationic dendrimers. These lipid/dendrimer hybrids consist of a low-generation, hydrophilic dendron (G2, G1, or G0) bonded to a hydrophobic tail. The G2-18C AD was reported to be an efficient siRNA vector with significant gene silencing. However, shorter tail ADs (G2-15C and G2-13C) and lower generation (G0 and G1) dendrimers failed as transfection carriers. To date, the self-assembly phenomenon of this class of amphiphilic dendrimers has not been molecularly explored using molecular simulation methods. To gain insight into these systems, the present study used coarse-grained molecular dynamics simulations to describe how ADs are able to self-assemble into an aggregate, and, specifically, how tail length and generation play a key role in this event. Finally, explanations are given for the better efficiency of G2/18-C as gene carrier in terms of binding of siRNA. This knowledge could be relevant for the design of novel, safer ADs with well-optimized affinity for siRNA.

Synthesis of Electroneutralized Amphiphilic Copolymers with Peptide Dendrons for Intramuscular Gene Delivery

Intramuscular gene delivery materials are of great importance in plasmid-based gene therapy system, but there is limited information so far on how to design and synthesize them. A previous study showed that the peptide dendron-based triblock copolymer with its components arranged in a reversed biomembrane architecture could significantly increase intramuscular gene delivery and expression. Herein, we wonder whether copolymers with biomembrane-mimicking arrangement may have similar function on intramuscular gene delivery. Meanwhile, it is of great significance to uncover the influence of electric charge and molecular structure on the function of the copolymers. To address the issues, amphiphilic triblock copolymers arranged in hydrophilic-hydrophobic-hydrophilic structure were constructed despite the paradoxical characteristics and difficulties in synthesizing such hydrophilic but electroneutral molecules. The as-prepared two copolymers, dendronG2(l-lysine-OH)-poly propylene glycol2k(PPG2k)-dendronG2(l-lysine-OH) (rL2PL2) and dendronG3(l-lysine-OH)-PPG2k-dendronG3(l-lysine-OH) (rL3PL3), were in similar structure but had different hydrophilic components and surface charges, thus leading to different capabilities in gene delivery and expression in skeletal muscle. rL2PL2 was more efficient than Pluronic L64 and rL3PL3 when mediating luciferase, β-galactosidase, and fluorescent protein expressions. Furthermore, rL2PL2-mediated growth-hormone-releasing hormone expression could significantly induce mouse body weight increase in the first 21 days after injection. In addition, both rL2PL2 and rL3PL3 showed good in vivo biosafety in local and systemic administration. Altogether, rL2PL2-mediated gene expression in skeletal muscle exhibited applicable potential for gene therapy. The study revealed that the molecular structure and electric charge were critical factors governing the function of the copolymers for intramuscular gene delivery. It can be concluded that, combined with the previous study, both structural arrangements either reverse or similar to the biomembrane are effective in designing such copolymers. It also provides an innovative way in designing and synthesizing new electroneutralized triblock copolymers, which could be used safely and efficiently for intramuscular gene delivery.

Screening of efficient siRNA carriers in a library of surface-engineered dendrimers

Polymers are widely used as non-viral carriers for siRNA delivery, but concern has also arisen in their limited efficacy and inherent toxicity. Whilst many of previous efforts have been documented towards improving the performance of polymers via chemical modifications, the structure-activity relationships (SAR) of these ligand-modified polymers are not well understood. To address this issue, we systemically prepared a library of surface-engineered dendrimers (>300) as the screening pool to discover efficient siRNA carriers. The modified ligands include alkyls and fluoroalkyls, amino acids, benzene derivatives and heterocyclic compounds. Gene silencing results showed that the lead material shows excellent efficacy even in hard-to-transfect cells such as mesenchymal stem cells. The SAR studies revealed that ligands containing appropriate hydrophobicity, or ligands with both hydrophobic and functional atoms/groups are essential for polymers to achive efficient knockdown efficacy. A second-generation library designed based on the above principles further confirms the proposed design criteria. The results enable the future rational design of potent siRNA carriers.

One-step Conjugation of Glycyrrhetinic Acid to Cationic Polymers for High-performance Gene Delivery to Cultured Liver Cell

Gene therapies represent a promising therapeutic route for liver cancers, but major challenges remain in the design of safe and efficient gene-targeting delivery systems. For example, cationic polymers show good transfection efficiency as gene carriers, but are hindered by cytotoxicity and non-specific targeting. Here we report a versatile method of one-step conjugation of glycyrrhetinic acid (GA) to reduce cytotoxicity and improve the cultured liver cell -targeting capability of cationic polymers. We have explored a series of cationic polymer derivatives by coupling different ratios of GA to polypropylenimine (PPI) dendrimer. These new gene carriers (GA-PPI dendrimer) were systematically characterized by UV-vis,(1)H NMR titration, electron microscopy, zeta potential, dynamic light-scattering, gel electrophoresis, confocal microscopy and flow cytometry. We demonstrate that GA-PPI dendrimers can efficiently load and protect pDNA, via formation of nanostructured GA-PPI/pDNA polyplexes. With optimal GA substitution degree (6.31%), GA-PPI dendrimers deliver higher liver cell transfection efficiency (43.5% vs 22.3%) and lower cytotoxicity (94.3% vs 62.5%, cell viability) than the commercial bench-mark DNA carrier bPEI (25 kDa) with cultured liver model cells (HepG2). There results suggest that our new GA-PPI dendrimer are a promising candidate gene carrier for targeted liver cancer therapy.

Interaction studies reveal specific recognition of an anti-inflammatory polyphosphorhydrazone dendrimer by human monocytes

Dendrimers are nano-materials with perfectly defined structure and size, and multivalency properties that confer substantial advantages for biomedical applications. Previous work has shown that phosphorus-based polyphosphorhydrazone (PPH) dendrimers capped with azabisphosphonate (ABP) end groups have immuno-modulatory and anti-inflammatory properties leading to efficient therapeutic control of inflammatory diseases in animal models. These properties are mainly prompted through activation of monocytes. Here, we disclose new insights into the molecular mechanisms underlying the anti-inflammatory activation of human monocytes by ABP-capped PPH dendrimers. Following an interdisciplinary approach, we have characterized the physicochemical and biological behavior of the lead ABP dendrimer with model and cell membranes, and compared this experimental set of data to predictive computational modelling studies. The behavior of the ABP dendrimer was compared to the one of an isosteric analog dendrimer capped with twelve azabiscarboxylate (ABC) end groups instead of twelve ABP end groups. The ABC dendrimer displayed no biological activity on human monocytes, therefore it was considered as a negative control. In detail, we show that the ABP dendrimer can bind both non-specifically and specifically to the membrane of human monocytes. The specific binding leads to the internalization of the ABP dendrimer by human monocytes. On the contrary, the ABC dendrimer only interacts non-specifically with human monocytes and is not internalized. These data indicate that the bioactive ABP dendrimer is recognized by specific receptor(s) at the surface of human monocytes.

Poly(Propylene Imine) Dendrimers and Amoxicillin as Dual-Action Antibacterial Agents

Besides acting as antimicrobial compounds, dendrimers can be considered as agents that improve the therapeutic effectiveness of existing antibiotics. In this work we present a new approach to using amoxicillin (AMX) against reference strains of common Gram-negative pathogens, alone and in combination with poly(propylene imine) (PPI) dendrimers, or derivatives thereof, in which 100% of the available hydrogen atoms are substituted with maltose (PPI 100%malG3). The concentrations of dendrimers used remained in the range non-toxic to eukaryotic cells. The results indicate that PPI dendrimers significantly enhance the antibacterial effect of amoxicillin alone, allowing antibiotic doses to be reduced. It is important to reduce doses of amoxicillin because its widespread use in medicine could lead to the development of bacterial resistance and environmental pollution. This is the first report on the combined antibacterial activity of PPI surface-modified maltose dendrimers and amoxicillin.

PAMAM Dendron Lipid Assemblies That Undergo Structural Transition in Response to Weakly Acidic pH and Their Cytoplasmic Delivery Capability

Dendron lipids designed to consist of amine-terminated polyamidoamine G1 dendron and two octadecyl chains were used for the preparation of pH-responsive molecular assemblies having phase structures that are changed through their dynamic molecular shape. The dendron lipid contains two primary amines and two tertiary amines in the dendron moiety, changing its charged state in the pH region between pH 10 and pH 4. The assemblies were shown to take a vesicle structure at neutral and alkaline pHs, but their structure changed to a micelle-like structure below pH 6.4. Because this pH region corresponds to one in which tertiary amines of the dendron lipid became protonated, protonation of tertiary amines in addition to primary amines in the dendron moiety might affect its dynamic molecular shape, resulting in a sharp pH response of the assemblies. The assemblies tended to form aggregates when taking on a vesicle form with a gel phase, but incorporation of a poly(ethylene glycol)-lipid provided dendron lipid vesicles with both sharp pH response and high colloidal stability. The poly(ethylene glycol)-incorporated dendron lipid vesicles tightly retained ovalbumin molecules in their internal aqueous space but released them almost completely at pH 6.0. In addition, the vesicles were shown to achieve efficient ovalbumin delivery into cytosol of DC2.4 cells (mouse dendritic cell line) after internalization through endocytosis.

Dendrimeric anticancer prodrugs for targeted delivery of ursolic acid to folate receptor-expressing cancer cells: synthesis and biological evaluation

The anticancer efficacy of ursolic acid (UA) was limited by poor water solubility, non-specific tumor distribution, and low bioavailability. To overcome this problem, polyamidoamine (PAMAM) conjugated with UA and folic acid (FA) as novel dendrimeric prodrugs were designed and successfully synthesized by a concise one-pot synthetic approach. Both FA and UA were covalently conjugated to the surface of PAMAM through acid-labile ester bonds and the covalently linked UA could be hydrolysed either in acidic (pH 5.4) or in neutral (pH 7.4) PBS solution. The cellular uptake study indicated that the presence of FA enhanced uptake of the dendrimeric prodrugs in folate receptor (FR) over-expressing Hela cells. The enhanced cellular uptake could be due to the electrostatic absorptive endocytosis and FR-mediated endocytosis. In contrast, for HepG2 cells, a FR-negative cell line, FA conjugation on the surface of the dendrimer showed no effect on the cellular uptake. In MTT assay and cell cycle analysis, FA-modified dendrimeric prodrugs showed significantly enhanced toxicity than non-FA-modified ones in Hela cells. These results suggested that FA-modified dendrimeric UA prodrugs have the potential for targeted delivery of UA into cancer cells to improve its anti-tumor efficacy.

Affinity enhancement by dendritic side chains in synthetic carbohydrate receptors

Dendritic side chains have been used to modify the binding environment in anthracene-based synthetic carbohydrate receptors. Control of length, charge, and branching enabled the positioning of side-chain carboxylate groups in such a way that they assisted in binding substrates rather than blocking the cavity. Conformational degeneracy in the dendrimers resulted in effective preorganization despite the flexibility of the system. Strong binding was observed to glucosammonium ions in water, with Ka values up to 7000 M(-1) . Affinities for uncharged substrates (glucose and N-acetylglucosamine) were also enhanced, despite competition from solvent and the absence of electrostatic interactions.

Next-generation sequencing reveals low-dose effects of cationic dendrimers in primary human bronchial epithelial cells

Gene expression profiling has developed rapidly in recent years with the advent of deep sequencing technologies such as RNA sequencing (RNA Seq) and could be harnessed to predict and define mechanisms of toxicity of chemicals and nanomaterials. However, the full potential of these technologies in (nano)toxicology is yet to be realized. Here, we show that systems biology approaches can uncover mechanisms underlying cellular responses to nanomaterials. Using RNA Seq and computational approaches, we found that cationic poly(amidoamine) dendrimers (PAMAM-NH2) are capable of triggering down-regulation of cell-cycle-related genes in primary human bronchial epithelial cells at doses that do not elicit acute cytotoxicity, as demonstrated using conventional cell viability assays, while gene transcription was not affected by neutral PAMAM-OH dendrimers. The PAMAMs were internalized in an active manner by lung cells and localized mainly in lysosomes; amine-terminated dendrimers were internalized more efficiently when compared to the hydroxyl-terminated dendrimers. Upstream regulator analysis implicated NF-κB as a putative transcriptional regulator, and subsequent cell-based assays confirmed that PAMAM-NH2 caused NF-κB-dependent cell cycle arrest. However, PAMAM-NH2 did not affect cell cycle progression in the human A549 adenocarcinoma cell line. These results demonstrate the feasibility of applying systems biology approaches to predict cellular responses to nanomaterials and highlight the importance of using relevant (primary) cell models.

Mechanisms and implications of dual-acting methotrexate in folate-targeted nanotherapeutic delivery

The rational design of a nanoplatform in drug delivery plays a crucial role in determining its targeting specificity and efficacy in vivo. A conventional approach relies on the surface conjugation of a nanometer-sized particle with two functionally distinct types of molecules, one as a targeting ligand, and the other as a therapeutic agent to be delivered to the diseased cell. However, an alternative simplified approach can be used, in which a single type of molecule displaying dual function as both a targeting ligand and therapeutic agent is conjugated to the nanoparticle. In this review, we evaluate the validity of this new strategy by using methotrexate, which displays multifunctional mechanisms of action. Methotrexate binds to the folate receptor, a surface biomarker frequently overexpressed in tumor cells, and also inhibits dihydrofolate reductase, an enzyme critical for cell survival and division. Thus we describe a series of fifth generation poly(amido amine) dendrimers conjugated with methotrexate, and discuss several lines of evidence supporting the efficacy of this new platform strategy based on surface plasmon resonance spectroscopy, enzyme activity assays, and cell-based studies with folate receptor (+) KB cancer cells.

Characterizing the interactions of organic nanoparticles with renal epithelial cells in vivo

Nanotechnology approaches are actively being pursued for drug delivery, novel diagnostics, implantable devices, and consumer products. While considerable research has been performed on the effects of these materials on targeted tumor or phagocytic cells, relatively little is known about their effects on renal cells. This becomes critical for supersmall nanoparticles (<10 nm), designed to be renally excreted. The active endocytic machinery of kidney proximal tubules avidly internalizes filtered proteins, which may also be the case for filtered nanoparticles. To test whether such interactions affect kidney function, we injected mice with either 5 nm dextran-based nanoparticles (DNP) that are similar in composition to FDA-approved materials or poly(amido amine) dendrimer nanoparticles (PNP) of comparable size. These fluorescently tagged nanoparticles were both filtered and internalized by renal tubular epithelial cells in a dose- and time-dependent fashion. The biological effects were quantitated by immunocytochemistry, measuring kidney injury markers and performing functional tests. DNP administration resulted in a dose-dependent increase in urinary output, while cellular albumin endocytosis was increased. The expression of megalin, a receptor involved in albumin uptake, was also increased, but AQP1 expression was unaffected. The effects after PNP administration were similar but additionally resulted in increased clathrin expression and increased endocytosis of dextran. We conclude that there are no major detrimental renal effects of DNP on overall kidney function, but changes in endocytosis-mediating protein expression do occur. These studies provide a framework for the testing of additional nanoparticle preparations as they become available.

RGD peptide-modified multifunctional dendrimer platform for drug encapsulation and targeted inhibition of cancer cells

Development of multifunctional nanoscale drug-delivery systems for targeted cancer therapy still remains a great challenge. Here, we report the synthesis of cyclic arginine-glycine-aspartic acid (RGD) peptide-conjugated generation 5 (G5) poly(amidoamine) dendrimers for anticancer drug encapsulation and targeted therapy of cancer cells overexpressing αvβ3 integrins. In this study, amine-terminated G5 dendrimers were used as a platform to be sequentially modified with fluorescein isothiocyanate (FI) via a thiourea linkage and RGD peptide via a polyethylene glycol (PEG) spacer, followed by acetylation of the remaining dendrimer terminal amines. The developed multifunctional dendrimer platform (G5.NHAc-FI-PEG-RGD) was then used to encapsulate an anticancer drug doxorubicin (DOX). We show that approximately six DOX molecules are able to be encapsulated within each dendrimer platform. The formed complexes are water-soluble, stable, and able to release DOX in a sustained manner. One- and two-dimensional NMR techniques were applied to investigate the interaction between dendrimers and DOX, and the impact of the environmental pH on the release rate of DOX from the dendrimer/DOX complexes was also explored. Furthermore, cell biological studies demonstrate that the encapsulation of DOX within the G5.NHAc-FI-PEG-RGD dendrimers does not compromise the anticancer activity of DOX and that the therapeutic efficacy of the dendrimer/DOX complexes is solely related to the encapsulated DOX drug. Importantly, thanks to the role played by RGD-mediated targeting, the developed dendrimer/drug complexes are able to specifically target αvβ3 integrin-overexpressing cancer cells and display specific therapeutic efficacy to the target cells. The developed RGD peptide-targeted multifunctional dendrimers may thus be used as a versatile platform for targeted therapy of different types of αvβ3 integrin-overexpressing cancer cells.

Recent advances in dendrimer-based nanovectors for tumor-targeted drug and gene delivery

Advances in the application of nanotechnology in medicine have given rise to multifunctional smart nanocarriers that can be engineered with tunable physicochemical characteristics to deliver one or more therapeutic agent(s) safely and selectively to cancer cells, including intracellular organelle-specific targeting. Dendrimers having properties resembling biomolecules, with well-defined 3D nanopolymeric architectures, are emerging as a highly attractive class of drug and gene delivery vector. The presence of numerous peripheral functional groups on hyperbranched dendrimers affords efficient conjugation of targeting ligands and biomarkers that can recognize and bind to receptors overexpressed on cancer cells for tumor-cell-specific delivery. The present review compiles the recent advances in dendrimer-mediated drug and gene delivery to tumors by passive and active targeting principles with illustrative examples.